Smooth blocks-based blind watermarking algorithm in compressed DCT domain

A novel blind watermarking scheme based on smooth blocks in compressed DCT domain is proposed. The smooth blocks are detected by a criterion which uses a relation between the quantized DC coefficients and the variance of AC coefficients in the block and deduced from the Weber's Law. In the approach, the watermark is embedded by modifying the average value of some low-frequency DCT coefficients in selected blocks, and recovered by the sign of the mean value of corresponding coefficients in detected blocks and there is no need for original image. The experimental results demonstrate that almost no perceptible distortion is found in the watermarked images, and the watermark is robust to some image processing operations such as scaling, noise, filtering and JPEG compression.